For the ganache: Put the chocolate in a heatproof bowl. Bring the heavy cream and salt to a gentle simmer in a saucepan over medium heat; pour over the chocolate and let sit until completely melted, about 5 minutes. Whisk until smooth. Whisk in the rum and coconut oil and stir until the ganache is smooth and shiny.
For the s'mores: Line a baking sheet with parchment paper and fit with a wire rack. Dip half of each graham cracker in the ganache and lay on the rack. Skewer a marshmallow and toast with a pastry torch. Place onto the ganache topped chocolate graham. Repeat with the remaining marshmallows and graham crackers.
For the isomalt flames: Add the red and yellow isomalt to separate small silicone or microwave-safe bowls and microwave until melted, about 1 minute. Let the isomalt cool off a bit before working with it. Spoon about 1 tablespoon of yellow isomalt onto a silicon-baking mat. Add a teaspoon of red isomalt and use a spoon to swirl. With heatproof gloves, pull off a small piece, roll into a tear drop shape and gently twist and pull into a flame-like piece. Repeat until there are 8 pieces.
Stick 1 isomalt flame into each of the marshmallows and serve.